Anchiornis and the temporal paradox

So after the original Anchiornis paper and now the follow up things should be pretty clear about the identity of this animal – it’s a troodontid that looks an awful lot like a basal bird. This is no surprise given that birds and troodontids are very close relatives and that Anchiornis is an especially basal troodontid and thus is probably closer in appearance to other basal birds than many others of its kind, and of course the original specimen in lacking a head did not have all the characters that might have helped us solve this earlier. So now onto the issue of time and evolution which is nicely demonstrated here by the new find – the oft quoted and very misleading temporal paradox.

If you have not met ghost lineages before then you can check out this nice little post here that I did on the subject as an introduction. As a micro-recap these are situations where we have a taxon in the fossil record which according to our understanding of its relationships should be pretty old, but we only find fossils of it in much more recent rocks, the ‘gap’ being the ghost lineage where we believe it to exist but cannot find it.

Modified from Hu et al., 2009 showing Anchiornis fill in the temporal gap between other maniraptorans and Archaeopteryx.

In the case of the earliest birds we do of course have Archaeopteryx in the later Late Jurassic rocks of Germany and then various other birds appearing in the Early Cretaceous and more recently than this. However, the closest relatives to birds according to our analyses are dromaeosaurs and troodontids, and a little further down the tree are things like oviraptorosaurs and alvarezsaurs (among others). But these taxa only currently appear in the latest Jurassic or the Early Cretaceous, significantly after Archaeopteryx first appears. Thus we have a ghost lineage with these various theropods having (we infer) appeared sometime in the Middle or early part of the Late Jurassic and then birds appearing but the only record (apart form a few hard to identify teeth) being Archaeopteryx itself. In short, if our hypothesis of bird ancestry is correct we really should see some of these other lineages appearing well before Archaeopteryx and until now, did not. This problem has been termed the ‘temporal paradox’ by the BAND group who maintain that this is evidence against a dinosaur origin for birds (despite the obvious caveat that this is true they then have to account for an absence of birds going back to the Triassic which is tens of millions of years a bigger gap – oh).

Until now of course, because since Anchiornis is now identified as a troodontid and the specimens that have been recovered (the original and the newly described one) from the early Late Jurassic and thus predate Archaeopteryx. This of course does not entirely eliminate the problem (we would still really like some old oviraptorosaurs and dromaeosaurs for starters) but it does demonstrate that the gap is far smaller than stated and does show a definitive troodontid that predates birds. As such hopefully the already unstable and rather unreasonable temporal paradox can finally leave these shores and not rear its head again (unless someone finds an Early Jurassic bird of course in which case we get to start again).

Well there is that, yes. But I think that just shows off the general problems with having an apparently large and rapid radiation (maniraptorans) with a pretty long ghost lineage. Whenever you suddenly stick in a new taxon you’ll likely improve one part and worsen another. It says more about the patchiness of small animals in the fossil record than the problems of ghost lineages I think.

We don’t necessarily need ‘Solnhofen’ type rocks to preserve them (only to get feathers), any good fossil bearing layer should be OK) but the truth is there are very few Middle Jurassic beds out there that we know of. Unless geologists can provide us with new possible sites of the right age, fossil bearing and from terrestrail environments we won’t have anywhere new to dig. Plus of course the likely issue that early maniraptorans were small and few in number will likely make them very rare in the fossil record. It will come in time, but don’t wait up for it!

Well it IS a theirizinosaur, but the exact age is questionable. It comes from a place where (as I recall) both Middle Jurassic and Early Cretaceous beds come together and no-one is exactly sure where it was collected. One of the original people on the expedition that found it says it came from the Jurassic beds, but the matrix still adhered to the specimen and the nature of the preservation suggests that it is from the Cretaceous. As such it’s a controversial specimen with no clear origin. It was even controversial for a while as to whether or not it was even a theirizinosaur, which at least now seems agreed upon.

“In short, if our hypothesis of bird ancestry is correct we really should see some of these other lineages appearing well before Archaeopteryx and until now, did not. This problem has been termed the ‘temporal paradox’ by the BAND group who maintain that this is evidence against a dinosaur origin for birds (despite the obvious caveat that this is true they then have to account for an absence of birds going back to the Triassic which is tens of millions of years a bigger gap – oh).”

The fact that you don’t see bird-like theropods older than Archaeopteryx is good evidence that they just don’t exist. For the same reason, we don’t find hominid fossils in the Jurassic either. Besides, it is customary for the cladists to conflate temporal paradox with fossil gap. They are not the same. Prior to the discovery of Tiktaalik, there is a definite gap between Acanthostega and the fishes, but there is no temporal paradox. If Acanthostega is found in an earlier strata than Tiktaalik, then there would be a definite temporal paradox. As it turned out Tiktaalik fits neatly between fishes that look like tetrapods and the earliest tetrapods. Hence there is a fossil gap but no temporal paradox.

There is also a gap between Longisquama, the first known reptile to have feathers, and Archaeopteryx, and the gap is admittedly considerable. But it is a gap, similar to the gap between fish and tetrapod, and it is being partially filled by Anchiornis. Anchiornis does nothing to eliminate or even reduce the temporal paradox facing the proponents of the dinosaurian origin of birds. In fact, the findings of feathers in a small arboreal animal older than Archaeopteryx means that the temporal paradox has increased another 10 million years or so. Labeling Anchiornis a troodontid does nothing for the temporal paradox, because Anchiornis looks nothing like Troodon.

Troodon is not arboreal and it certainly cannot have feathers sticking out of its legs because that would have interfered with its running. Could an animal like Troodon have given rise to Anchiornis via a ghost lineage? That is what your cladogram is suggesting. The problem of course is that Troodon is a Cretaceous theropod.

If not, then perhaps animals like Troodon actually descended from an animal like Anchiornis. Troodon was, therefore, a flightless bird. That also means that dinosaurs (at least some of them) are in fact flightless birds and that the Dinosauria is polyphyletic. Unfortunately, even that alternative (unappetizing though it may be) is unlikely, because we now know that theropod dinosaurs could not have evolved from birds, because birds have fixed thigh bones that cannot be rotated within the hip socket. Troodon, then, is a dinosaur that is only superficially similar to Anchiornis. But what else is new? Darwinian taxonomists have been telling the cladists that they rely on superficial similarities in their analyses for decades, but the cladists have ignored that criticism for an equally long period of time. There is definitely no temporal paradox between the Darwinian’s criticism and the cladists’ practice. It is contemporaneous.

“The fact that you don’t see bird-like theropods older than Archaeopteryx is good evidence that they just don’t exist. ”

Well, apart from Anchiornis, and Haplocheirus, and the scansoropterigids. And the presence of dromaeosaurs and troodontid like teeth that predate the body fossils of paravains.

And of course the obviously, well know and well documented baises in the fossil record.

So they do exist and there’s a good reason why they might be rare. As with your previous comments, you really don’t seem to have read up on the literature or understand the implications.

“Hence there is a fossil gap but no temporal paradox.”
But these is no fossil gap. There is a steady and continuious stream of character changes from basal archosaurs through to modern birds, all the way through the theropods. The temporal paradox was the concept of Alan Fedducis’a supporters and now you say it’s the creation of the birds are dinosaurs group? Eh?

“Longisquama, the first known reptile to have feathers,“
Well， that is enormously contentious at best and highly erroneous at worst.

“. Anchiornis does nothing to eliminate or even reduce the temporal paradox facing the proponents of the dinosaurian origin of birds. ”

How? It is part of the sister-taxon clade to birds and appears before birds? How can this NOT reduce the (alledged) paradox? It does, in fact, fit perfectly. And Haplocherius (basal maniraptoran in the Middle Jurasic) fits better. It fits our theory exactly.

“Labeling Anchiornis a troodontid does nothing for the temporal paradox, because Anchiornis looks nothing like Troodon.”
Read the paper. Read the characters. Look at the fossils. They are in the same clade because they share multiple, disagnostic, synapomoprhies in common. This is a nothing statement back by nothing.

“Could an animal like Troodon have given rise to Anchiornis via a ghost lineage?”
How does this work? Anchiornis is considered basal to other troodontids, so how would Troodon give rise to it? You say we have Anchiornis descending from Troodon and we don’t. The figure is right up there and you still try to misrepresent it. And since no Troodon specimen has been recovered with feathers we can’t know what it looks like in that sense. As with your previous comment, you are setting up a false position and then failing to knock it down. I wonder if you might be conflatig ‘troodontids’ with ‘Troodon’ which if so, only shows you dont understand taxonomy and / or are misreading the words on the figure. The only thing you are showing here is that you have not and cannot have read and / or understood the papers.

I’m not carrying on with this or any conversation like it. There is plenty of science out there (there’s even a guide on this blog as to how to read a phylogenetic tree, you would do well to read it). Read the science, understand the science, learn the science. But don’t try to pick a fight with something that you don’t get and waste my time in the process. You gross mischaracterisations of our position only show your ignorance, not our errors. If you want to discuss this then I suggest you head to the DML, or try to get your ideas published, but this is not the forum for this.

Please do not put inflamatory and un-supported statements on here. I have tried to explain things to you before and to give you information and direct you to relevant papers. Do not just show up on here with random statements or links back to your blog. If you carry on like this I will just delete them.

However, more critically is the fact that you are running a blog called ‘pterosaurnet’ which is an exceptionally obvious attempt to take credit for, or take the credibility of my own ‘pterosaur.net’ site and ‘pterosaur-net’ blog. This is unacceptable and you are not welcome here as a result.

You know full well that you have nothing to do with these sites at all and there is no reason at all to take such a name unless it is to try to appear to be connected with the others. I can’t stop you, but I can make it clear that this is inappropriate and you must know that.

A GER or MSM calculation for the Hu et al cladogram would be very interesting and very valuable.
It would give us some objective quantification of the fit between the cladogram and the fossil record.
It is surprising that nobody has thought to ask for it.

However, to be polite, yes it would be interesting. I am sure people have thought of it, but there are hundreds, even thousands of cladograms that could do with this kind of research and not everyone has time to do everything immediately. It might well have been done but not published yet – papers take years to come out and this is still a ‘new’ study.

Now, please leave, and please do something about that blog title of yours. It is not right.

You are clearly ignoring my posts. I have never had cause to ban anyone from this site before, those who have been asked to leave have done so. Please leave. Please do not comment on here again. If you continue to do so, your comments will be deleted and / or you will be banned.

More fascinating info about the ghost lineages and the temporal paradox:http://www.sciencemag.org/cgi/data/327/5965/571/DC1/1 (Page 71)
Jonah N. Choiniere,* Xing Xu, James M. Clark, Catherine A. Forster, Yu Guo, Fenglu Han
“Brochu and Norell (S71) refuted the ‘temporal paradox’ and the use of the stratigraphic record to falsify
prevailing hypotheses about the theropod origin of birds by showing that the theropod hypothesis
was more stratigraphically consistent than competing hypotheses for bird origins, such as a
crocodylomorphs sister group. Since the publication of Brochu and Norell, discoveries of new
fossil theropod taxa, particularly ones from China, have strengthened the morphological support
for a theropod-bird link (S1, S72-S74). These discoveries have not, however, greatly improved
the fit of the theropod stratigraphic record to the hypothesized phylogeny for these taxa, because
they are largely from Early Cretaceous or younger deposits. Other discoveries of theropods
within the temporal gap have improved stratigraphic sampling but not stratigraphic fit to the
phylogeny. For example, recent discoveries of scansoriopterygid taxa (S75, S23) from the
Jurassic Daohugou Formation (S54) potentially predate Archaeopteryx. The phylogenetic
position of these taxa is nested within Avialae, however, and therefore they increase the temporal
gap between Avialans and other paravians.